Alexandru Nichifor

Stability and competitive equilibrium in trading networks

We introduce a model in which agents in a network can trade via bilateral contracts. We find that when continuous transfers are allowed and utilities are quasi-linear, the full substitutability of preferences is sufficient to guarantee the existence of stable outcomes for any underlying network structure. Furthermore, the set of stable outcomes is essentially equivalent to the set of competitive equilibria, and all stable outcomes are in the core and are efficient. By contrast, for any domain of preferences strictly larger than that of full substitutability, the existence of stable outcomes and competitive equilibria cannot be guaranteed.

Consistency in one-sided assignment problems

One-sided assignment problems combine important features of two well-known matching models. First, as in roommate problems, any two agents can be matched and second, as in two-sided assignment problems, the division of payoffs to agents is flexible as part of the solution. We take a similar approach to one-sided assignment problems as Sasaki (Int J Game Theory 24:373–397, 1995) for two-sided assignment problems, and we analyze various desirable properties of solutions including consistency and weak pairwise-monotonicity. We show that for the class of solvable one-sided assignment problems (i.e., the subset of one-sided assignment problems with a non-empty core), if a subsolution of the core satisfies [Pareto indifference and consistency] or [invariance with respect to unmatching dummy pairs, continuity, and consistency], then it coincides with the core (Theorems 1 and 2). However, we also prove that on the class of all one-sided assignment problems (solvable or not), no solution satisfies consistency and coincides with the core whenever the core is non-empty (Theorem 4). Finally, we comment on the difficulty in obtaining further positive results for the class of solvable one-sided assignment problems in line with Sasaki’s (1995) characterizations of the core for two-sided assignment problems.

Intellectual Influence: Quality Versus Quantity

To take development and budgeting decisions for research activi- ties the officials in charge need to constantly evaluate and assess the quality of research. Over the years a handful of scoring methods for academic journals have been proposed. Discussing the most prominent methods (de facto standards) we show that they cannot distinguish quality from quantity at article level and that they are inherently biased against journals publishing more articles. If we consider the length of a journal by the number of pages or characters, then all methods are biased against lengthier journals. The systematic bias we nd is analytically tractable and implies that the methods are ma- nipulable. We show that the strategies for successful manipulation are relatively easy to infer and implement. The implications of our ndings extend beyond the evaluation of academic research, to related settings like the ranking of web domains. Non-manipulable methods for measuring intellectual in uence exist.